An electronic card chassis typically provides a number of card slots for inserting electronic equipment or application cards. These application cards are designed to perform functions such as providing modem card functions or other communication interface card functions. A communication backplane in the electronic card chassis provides the application cards a source of power and communication access through the card chassis. The communication backplane may include a plurality of different backplane communication buses to allow electronic circuit cards in the card chassis to communicate to external devices or to other cards in the card chassis.
In addition to the plurality of application cards capable of performing a variety of functions, the electronic card chassis may also contain a management card to perform system overhead management functions for the application cards in the chassis. A backplane communication bus allows the management card to communicate to the plurality of application cards. The communication bus provides management cards a communication path through the communication backplane to access each of the application cards in the card chassis.
To provide for fault tolerant operation, the card chassis may include a number of management cards for backup and redundancy in case of a failure of a primary management card. If a management card were to experience a failure, a second or backup management card could take over the management function of the application cards in the electronic card chassis.
In this redundant configuration including a plurality of management cards, each of the plurality management cards will typically have a backplane communication bus connection to each of the application cards. As a result of the plurality of management cards, each application card will have a plurality of backplane communication buses from which it may receive communications from the management cards at any time. As a consequence, the application card must be capable of receiving messages from any of the management cards over any one of the backplane communication buses accessing the card. Thus, to properly receive incoming management messages from any of the management cards, the application card must be able to dynamically switch between different backplane communication buses.